By 2050, the US beef industry must produce an extra 40 million tons of beef to satisfy the global demand, while reducing methane (CH4) emissions. This surplus of cattle will be provided mostly by cow-calf operations, which rely primarily on grazing. Those pastures are often infested with weeds such as pigweed (Amaranthus spinosus), one of the most invasive in the US, known for its increased polyphenols concentration. Despite the known effect of polyphenols on CH4 reduction, few studies have explored pigweed as a feed additive. Our objective was to evaluate the effect of in vitro addition of pigweed on ruminal fermentation, digestibility, and CH4 production. We collected ruminal fluid from three American Aberdeen steers (374 ± 21 kg) receiving a backgrounding diet (80:20% corn silage:cotton gin trash, as fed). We incubated (24 h, 39°C) diet (0.7 g) plus the inclusion of 0, 2.5, 5, or 10% (of diet DM) of roots, stems, leaves, seeds, or the whole pigweed plant (WHO). Volatile fatty acids (VFA), CH4 (mmol g-1 organic matter), ammonia, pH, gas, in vitro dry matter, and organic matter digestibility (IVDMD and IVOMD) were determined. Using the MIXED procedure of SAS, data were analyzed as a randomized complete block design with a 5 × 4 factorial arrangement of treatments with plant part (n = 5) and inclusion level (n = 4) as fixed main factors. Incubation and bottle within incubation were random effects. Polynomial orthogonal contrasts were used to determine linear, quadratic, and cubic effects of inclusion level. Plant × level interactions were detected in acetate, propionate, and butyric molar proportion, total VFA, CH4 production, and IVDMD (P < 0.01). Increasing levels of stems increased acetate concentration (P = 0.03), while those from WHO led to a linear reduction of acetate (P < 0.01). The inclusion of 2.5% of leaves, seeds, and WHO increased propionate concentration (P = 0.05), but greater levels decreased it (P < 0.01). Increasing levels of all parts decreased acetate:propionate proportion (P < 0.001). Increasing levels of WHO resulted in a linear reduction of CH4 production (P < 0.05), while increasing inclusion of roots and stems increased CH4 production (P < 0.01). Quadratic reductions in CH4 production were observed after increasing the addition of leaves, seeds, and WHO (P < 0.001). Increasing levels of leaves and roots decreased ammonia concentration (P < 0.01) while stems increased it (P = 0.01). Except for stems and roots, there was a linear decrease in IVDMD with increasing levels of all parts (P < 0.001). The inclusion of low levels of seeds, leaves, and WHO promoted ruminal changes leading to a reduction of CH4 production without significantly compromising the digestibility.

中文翻译：

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144 利用入侵性藜草（Amaranthus Spinosus）作为肉牛饲料中的新型甲烷减排策略：可持续方法

到 2050 年，美国牛肉行业必须额外生产 4000 万吨牛肉才能满足全球需求，同时减少甲烷 (CH4) 排放。这些剩余的牛将主要由主要依靠放牧的牛犊养殖提供。这些牧场经常长满杂草，例如苋菜（Amaranthus spinosus），这是美国最具入侵性的杂草之一，以其多酚浓度升高而闻名。尽管已知多酚对减少 CH4 的作用，但很少有研究探索猪草作为饲料添加剂。我们的目的是评估体外添加藜草对瘤胃发酵、消化率和 CH4 产生的影响。我们从三头美国阿伯丁公牛（374 ± 21 kg）中收集了瘤胃液，这些公牛接受背景饮食（80:20% 玉米青贮饲料：杜松子酒垃圾，按饲喂）。我们孵化（24 小时，39°C）饮食（0.7 克）加上 0%、2.5%、5% 或 10%（饮食 DM）的根、茎、叶、种子或整个猪草植物 (WHO) 。测定挥发性脂肪酸（VFA）、CH4（mmol g-1 有机物）、氨、pH、气体、体外干物质和有机物消化率（IVDMD 和 IVOMD）。使用 SAS 的 MIXED 程序，以随机完整区组设计的形式对数据进行分析，其中处理的 5 × 4 因子排列以植物部分 (n = 5) 和包含水平 (n = 4) 作为固定的主要因素。孵化和孵化期间的瓶子是随机效应。多项式正交对比用于确定包含水平的线性、二次和三次效应。在乙酸盐、丙酸盐和丁酸摩尔比例、总 VFA、CH4 产量和 IVDMD 中检测到植物 × 水平的相互作用（P < 0.01）。增加茎水平会增加乙酸盐浓度（P = 0.03），而来自 WHO 的茎水平则导致乙酸盐浓度线性降低（P < 0.01）。加入 2.5% 的叶子、种子和 WHO 会增加丙酸盐浓度 (P = 0.05)，但较高含量会降低丙酸盐浓度 (P < 0.01)。增加所有部分的水平降低了乙酸盐：丙酸盐的比例(P＜0.001)。WHO 水平的增加导致 CH4 产量线性减少（P < 0.05），而增加根和茎的含量则增加 CH4 产量（P < 0.01）。增加叶子、种子和 WHO 的添加量后，观察到 CH4 产量呈二次方减少（P < 0.001）。叶和根含量的增加降低了氨浓度（P < 0.01），而茎则增加了氨浓度（P = 0.01）。除茎和根外，各部位IVDMD均随含量增加呈线性下降趋势(P＜0.001)。低含量的种子、叶子和 WHO 的加入促进了瘤胃变化，导致 CH4 产量减少，而不会显着影响消化率。